Commit c10fcb14 authored May 05, 2016 by Wang YanQing Committed by Ingo Molnar May 05, 2016

x86/sysfb_efi: Fix valid BAR address range check



The code for checking whether a BAR address range is valid will break
out of the loop when a start address of 0x0 is encountered.

This behaviour is wrong since by breaking out of the loop we may miss
the BAR that describes the EFI frame buffer in a later iteration.

Because of this bug I can't use video=efifb: boot parameter to get
efifb on my new ThinkPad E550 for my old linux system hard disk with
3.10 kernel. In 3.10, efifb is the only choice due to DRM/I915 not
supporting the GPU.

This patch also add a trivial optimization to break out after we find
the frame buffer address range without testing later BARs.

Signed-off-by: Wang YanQing <udknight@gmail.com>
[ Rewrote changelog. ]
Signed-off-by: Matt Fleming <matt@codeblueprint.co.uk>
Reviewed-by: Peter Jones <pjones@redhat.com>
Cc: <stable@vger.kernel.org>
Cc: Ard Biesheuvel <ard.biesheuvel@linaro.org>
Cc: David Herrmann <dh.herrmann@gmail.com>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Thomas Gleixner <tglx@linutronix.de>
Cc: Tomi Valkeinen <tomi.valkeinen@ti.com>
Cc: linux-efi@vger.kernel.org
Link: http://lkml.kernel.org/r/1462454061-21561-2-git-send-email-matt@codeblueprint.co.uk


Signed-off-by: Ingo Molnar <mingo@kernel.org>

parent 7f9b474c

arch/x86/kernel/sysfb_efi.c

+12 −2

Original line number	Diff line number	Diff line
		@@ -106,14 +106,24 @@ static int __init efifb_set_system(const struct dmi_system_id *id)
		continue;
		for (i = 0; i < DEVICE_COUNT_RESOURCE; i++) {
		resource_size_t start, end;
		unsigned long flags;

		flags = pci_resource_flags(dev, i);
		if (!(flags & IORESOURCE_MEM))
		continue;

		if (flags & IORESOURCE_UNSET)
		continue;

		if (pci_resource_len(dev, i) == 0)
		continue;

		start = pci_resource_start(dev, i);
		if (start == 0)
		break;
		end = pci_resource_end(dev, i);
		if (screen_info.lfb_base >= start &&
		screen_info.lfb_base < end) {
		found_bar = 1;
		break;
		}
		}
		}

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